Induction of mucosal HIV-specific immune responses by vaccines may facilitate effective control of HIV or SIV replication at these sites. However, there is no effective HIV mucosal vaccine yet. This proposal is intend to identify effective orally administered immunogen, determine the optimal easy and effective immunization route, and uncover the mechanism of action whereby this vaccine can induce potent mucosal immune responses to protect from mucosal viral challenge. We have developed and characterized chimeric CD40 ligand/simian-human immunodeficiency (CD40L/SHIV) virus-like particles (VLPs) which possess the antigen presenting cell (APC) maturation signal CD40L. We have shown that this chimeric CD40L/SHIV VLPs has the ability to directly bind and activate dendritic cells (DC) in oral mucosa and local draining lymph nodes (LN). Compared with the already potent SHIV VLP vaccine, the chimeric CD40L/SHIV VLPs can induce as much as 4-fold higher mucosal IgA response and mucosal cytotoxic T lymphcytes (CTL) response via an oral sub-mucosal immunization route. At present, none of the VLP mucosal vaccine strategies have been shown to enact protective efficacy in nonhuman primate models. Based on these exciting preliminary data, we have developed our central hypothesis that oral submucosal injection of chimeric CD40L/SHIV VLPs, which possess the APC maturation signal CD40L, will directly bind and activate DCs in oral mucosa and local draining lymph nodes (LN), thereby initiating strong and effective systemic and mucosal immunity that will protect SHIV SF162P3 challenge in rhesus macaques. To test our hypothesis, we propose the following specific aims: Aim 1: Determine the optimal mCD40L/SHIV VLP oral sub-mucosal immunization regimen and characterizing mucosal immune responses in mice; Aim 2: Determine the immunogenicity and protective effect of hCD40L/SHIV VLP oral mucosal vaccination from pathological SHIVSF162P3 challenge in a non-human primate model; and Aim 3. Decipher the mechanism whereby hCD40L/SHIV VLP oral submucosal vaccination induces strong mucosal immune responses in mice and in non-human primates. The proposed project represents exploration of a novel antigen and immunization route for the purpose of developing an effective and safe chimeric SHIV VLP oral mucosal HIV vaccine. This study will also increase our understanding of oral mucosal immunity, which may contribute to future oral mucosal vaccine design. Our future goal is to move this promising strategy forward for an effective oral mucosal vaccine development for preventing AIDS.